NLM Policy on Subject Analysis and Classification - National Library ...

<strong>NLM</strong> <strong>Policy</strong> on Subject Analysis and Classification 

Table of Contents 

I. Introduction ..................................................................................................................................................... 4 

I.A. Philosophical bases of subject cataloging ......................................................................................... 4 

I.B. Functions of subject cataloging ......................................................................................................... 4 

II. Assigning Subject Headings ............................................................................................................................ 4 

II.A. Tools for Subject Analysis ................................................................................................................ 4 

1. Primary tools ....................................................................................................................... 4 

a. MeSH Browser ..................................................................................................... 4 

b. MeSH introductory documentation ...................................................................... 5 

c. Use of Medical Subject Headings ........................................................................ 5 

d. Cataloging course: Using Medical Subject Headings (MeSH®) in 

Cataloging ............................................................................................................ 5 

2. Secondary tools ................................................................................................................... 5 

a. Indexing Manual ................................................................................................... 5 

b. Technical Memoranda .......................................................................................... 6 

c. Technical notes ..................................................................................................... 6 

d. Online Indexing course ......................................................................................... 6 

3. Other resources ................................................................................................................... 6 

a. Dorland’s Medical Dictionary ............................................................................. 6 

b. Library of Congress Subject Cataloging Manual ................................................. 6 

II.B. General Policies ................................................................................................................................ 7 

1. When to assign subject headings ........................................................................................ 7 

2. Determination of primary/secondary subjects .................................................................... 7 

3. Order of subject headings ................................................................................................... 7 

4. MARC coding ..................................................................................................................... 7 

5. Transcription of MeSH headings ........................................................................................ 8 

II.C. Assigning MeSH Terms .................................................................................................................... 8 

1. General................................................................................................................................ 8 

a. Contents of the item.............................................................................................. 8 

b. Serials and multipart items ................................................................................... 8 

c. Broader or narrower relationships ........................................................................ 8 

d. Assigning the same MeSH term ........................................................................... 9 

e. Audience ............................................................................................................... 9 

f. Patient care terms ................................................................................................. 9 

2. Main headings ..................................................................................................................... 9 

a. General ................................................................................................................. 9 

b. Rule of three ....................................................................................................... 10 

c. Diseases vs. specialty ......................................................................................... 10 

d. Pre-coordinated organ-disease terms .................................................................. 10 

e. Diseases vs. organisms ....................................................................................... 11 

f. Biographies ......................................................................................................... 11 

g. History ................................................................................................................ 11 

h. MeSH annotations (General) .............................................................................. 12 

i. Pharmacologic actions ........................................................................................ 12 

j. Supplementary concept records (SCRs) ............................................................. 13 

k. Age groups ......................................................................................................... 13 

Effective Date: 11/09/1995 Page 1 of 46 Last Updated: 07/27/2010

3. Topical qualifiers/subheadings ......................................................................................... 14 

a. General ............................................................................................................... 14 

b. Allowable qualifiers (AQs) ................................................................................ 14 

c. Entry combinations ............................................................................................. 15 

d. Annotations about qualifiers/subheadings .......................................................... 15 

e. Common subheading coordinations ................................................................... 15 

f. Use of adverse effects, poisoning, and toxicity ................................................... 15 

g. Use of epidemiology and ethnology ................................................................... 15 

h. Use of legislation & jurisprudence .................................................................... 16 

i. Use of history ..................................................................................................... 16 

j. Use of metabolism, pharmacokinetics, and pharmacology ................................ 17 

k. Use of statistics & numerical data ..................................................................... 17 

l. Use of radiography, radionuclide imaging, surgery, and 

ultrasonography ................................................................................................. 18 

m. Coordinating a general subheading with a more specific main heading ............. 18 

4. Geographics ...................................................................................................................... 18 

5. Genre/publication type headings (PTs) ............................................................................. 18 

a. General ............................................................................................................... 18 

b. Annotations and scope notes for publication types ............................................ 19 

c. Multiple publication types .................................................................................. 19 

d. Use of $9 n with publication types ..................................................................... 19 

e. Special instructions for use of selected publication types .................................. 20 

6. Language subheadings ...................................................................................................... 22 

II.D. Assigning Other Subject Added Entries.......................................................................................... 22 

1. General.............................................................................................................................. 22 

a. Names/uniform titles from Name Authority File (NAF) .................................... 22 

b. Use of topical subheadings with names/uniform titles ....................................... 22 

c. Coordination of names/uniform titles and MeSH ............................................... 22 

2. Personal names ................................................................................................................. 23 

3. Corporate names ............................................................................................................... 23 

4. Conference names ............................................................................................................. 24 

5. Uniform titles and name/title entries ................................................................................. 24 

6. Geographic names ............................................................................................................ 24 

II.E. Special Situations in Subject Cataloging ........................................................................................ 24 

1. Editions ............................................................................................................................. 24 

2. Translations ...................................................................................................................... 25 

II.F. <strong>NLM</strong> Subject Analysis -- Historical Practices and Changes ........................................................... 25 

1. Assignment of subject headings........................................................................................ 25 

2. Order and priority of subject headings .............................................................................. 26 

3. Change to internal structure of subject strings .................................................................. 26 

4. Notable changes in subject analysis practice since 2006 .................................................. 27 

III. Assigning Classification ................................................................................................................................ 27 

III.A. Basic Tools...................................................................................................................................... 27 

1. National Library of Medicine Classification .................................................................... 27 

2. Library of Congress Classification Schedule .................................................................... 28 

3. Classification Course: Cataloging: Fundamentals of the <strong>NLM</strong>® Classification .............. 28 

III.B. Basic Rules...................................................................................................................................... 28 

1. When to assign classification numbers ............................................................................. 28 

2. Principles of classification ................................................................................................ 29 

a. General ............................................................................................................... 29 

b. Classification by disease, region, organ ............................................................. 29 

c. Choosing between the <strong>NLM</strong> and LC Classification schedules ........................... 29 

d. Pediatrics ............................................................................................................ 30 

e. Humans vs. animals ............................................................................................ 30 


f. Reversal of a medical procedure ........................................................................ 30 

g. Biography vs. autobiography .............................................................................. 31 

h. Verification of class numbers in the index ......................................................... 31 

i. Geographic subdivision ...................................................................................... 31 

3. Structure of the classification number and MARC coding ............................................... 31 

III.C. General Procedures for Assigning the Classification Number ........................................................ 32 

1. Using the class schedule index ......................................................................................... 32 

a. Specific concepts ................................................................................................ 32 

b. General concepts ................................................................................................ 32 

c. Classification modified by topical subheading ................................................... 32 

d. Topics coordinated with age groups and pregnancy ........................................... 33 

e. Applying geographic subdivision ....................................................................... 33 

f. Using LC classification numbers referenced in the <strong>NLM</strong> Classification 

index ................................................................................................................... 34 

III.D. Selecting a Class Number When the MeSH term is Not Listed in the <strong>NLM</strong> Class Index............... 35 

1. Using the MeSH tree structures ........................................................................................ 35 

a. General ............................................................................................................... 35 

b. Drugs and chemicals........................................................................................... 36 

2. Using the LC Classification schedule ............................................................................... 36 

III.E. Special Rules ................................................................................................................................... 37 

1. Bibliographies, abstracts, and indexes .............................................................................. 37 

2. General guidelines for the use of form numbers ............................................................... 37 

3. Special Instructions for classification of Legislation and Statistics .................................. 39 

a. Legislation .......................................................................................................... 39 

b. Statistics ............................................................................................................. 40 

4. Serial publications ............................................................................................................ 40 

5. Serial analytics .................................................................................................................. 41 

6. Works on historical aspects of subjects ............................................................................ 41 

7. WZ Schedule .................................................................................................................... 42 

8. 19th Century Schedule ...................................................................................................... 42 

9. Nursing materials .............................................................................................................. 43 

10. Documents on microform ................................................................................................. 43 

11. Electronic resources .......................................................................................................... 43 

12. Editions ............................................................................................................................. 43 

13. Translations ...................................................................................................................... 44 

14. Reprints ............................................................................................................................. 44 

15. Supplements ...................................................................................................................... 44 

III.F. <strong>NLM</strong> Classification Assignment – Historical Practices and Changes ............................................ 45 

1. W3 .................................................................................................................................... 45 

2. WY ................................................................................................................................... 45 

3. Shelflisting ........................................................................................................................ 45 


I. Introduction 

I.A. Philosophical bases of subject cataloging 

Subject cataloging, like many library activities, is concerned mainly with organizing knowledge for 

effective use. The cataloger first determines the significant characteristics of a work and then translates 

the subject content into terms of the systems being used -- the notation of the classification scheme and 

terms selected from the library’s authorized subject vocabulary. The nature of the work and library’s 

policies guide the cataloger's decisions regarding specificity and depth of analysis and the individual 

library's organizing schemes determine the labels that are assigned to each item for the user. 

I.B. Functions of subject cataloging 

The consistent application of subject headings and classification numbers is essential for orderly access to 

the collection and easy retrieval of similar materials. There are many ways in which to gather similar 

documents together: for instance, by topic ("What is it about?"); by publication type ("What genre or 

format is it?"); or by field of interest ("What is it for?"). The subject cataloger must decide which aspect is 

most important and useful, and assign subject headings and classification accordingly. 

II. Assigning Subject Headings 

II.A. Tools for Subject Analysis 

1. Primary tools 

MeSH (http://www.nlm.nih.gov/pubs/factsheets/mesh.html), the National Library of Medicine’s 

controlled medical vocabulary thesaurus, is the primary tool used in subject analysis. It may be accessed 

online using the MeSH Browser (http://www.nlm.nih.gov/mesh/MBrowser.html). 

a. MeSH Browser 

The MeSH Browser (http://www.nlm.nih.gov/mesh/MBrowser.html) contains the complete MeSH 

medical vocabulary, additional cross references or entry terms, chemical names mapped to appropriate 

MeSH terms, scope notes or definitions for most MeSH terms, a list of allowable qualifiers (AQs) or topical 

subheadings which may be used with each term, as well as hot links to relevant sections of the Indexing 

Manual and Technical Notes (see below). There is a separate unit record for each MeSH term or 

descriptor. Additionally, each term is listed in a hierarchal “tree” structure 

(http://www.nlm.nih.gov/mesh/trees.html), arranged from the most general to the most specific concept 

under broad subject categories. 


. MeSH introductory documentation 

The Introduction to MeSH (http://www.nlm.nih.gov/mesh/introduction.html), accessible from the MeSH 

Home Page (http://www.nlm.nih.gov/mesh/), provides links to documentation explaining how the MeSH 

vocabulary is to be used and how to interpret the MeSH unit record. It also lists terms that have been 

added, deleted, or modified for the current year. 

c. Use of Medical Subject Headings 

The Use of Medical Subject Headings for Cataloging (http://www.nlm.nih.gov/mesh/catpractices.html) 

section of the Introduction to MeSH includes specific instructions for catalogers regarding the correct 

coordination of descriptors and subheadings, interpretation of the cataloging annotations in the MeSH 

record, and assignment of publication types. 

Also included are instructions on how to construct a traditional subject heading string from subject 

headings as they appear in <strong>NLM</strong>’s online public access catalog. 

d. Cataloging course: Using Medical Subject Headings (MeSH®) in Cataloging 

The course (http://www.nlm.nih.gov/tsd/cataloging/trainingcourses/mesh/index.html) is a free set of 

modules and interactive exercises that students may take at their own pace without an instructor. The 

course covers the use of MeSH in the cataloging environment and is divided into eight modules: Subject 

Analysis Principles, Introduction to Medical Subject Headings (MeSH) and the MeSH Browser, Selecting 

the Main Concept, Use of Topical Subheadings in MeSH, Geographic Headings, Publication Types, Names 

as Subject, and Deconstructed Headings vs. Subject Strings. 

2. Secondary tools 

a. Indexing Manual 

This manual outlines the general procedures followed in the subject analysis of articles in journals indexed 

by <strong>NLM</strong>. The Cataloging Section generally follows the Indexing Section's policies for assigning subject 

headings, to the extent possible and practicable. Therefore, many chapters of the Indexing Manual (e.g., 

Chapter 19, "Subheadings") are also useful and informative for catalogers. The MeSH Browser provides 

links to the Indexing Manual in the format “Manual 19.7”, and generally provides a hot link to the 

relevant chapter. The entire Indexing Manual is available to <strong>NLM</strong> staff at 

http://www.nlm.nih.gov/internal/mesh/indexingmanual. 


. Technical Memoranda 

These communications to Indexing Section staff augment the annotations found in the MeSH Browser and 

assist catalogers as well with the correct application of specific subject headings. They are stored online as 

part of the Indexing Manual. The Technical Memoranda are available to <strong>NLM</strong> staff at 

http://www.nlm.nih.gov/internal/mesh/indexingmanual. 

c. Technical notes 

These documents discuss practices relating to groups of concepts, and are intended to contain more 

specific information than that presented in the Indexing Manual, while not duplicating the detailed 

guidelines available in MeSH annotations. The MeSH Browser provides references to the technical notes 

in the format "TN 228." 

Note: Technical Notes are no longer being issued. Information from existing Technical Notes is being 

incorporated into the Indexing Manual as resources permit. However, the current MeSH Browser 

continues to include references to relevant existing Technical Notes. 

d. Online Indexing course 

The course is a free set of modules and interactive exercises that students may take at their own pace 

without an instructor. The course covers the indexing principles and procedures followed in the subject 

analysis of articles in journals indexed by <strong>NLM</strong>. The Online Indexing Course is available to <strong>NLM</strong> staff at 

http://www.nlm.nih.gov/internal/bsd/index_section/training/online_indexing_class/USE_010.htm 

3. Other resources 

a. Dorland’s Medical Dictionary 

This dictionary provides the spelling, meaning, and derivation of specific medical terms. 

b. Library of Congress Subject Cataloging Manual 

This manual, available online as part of the “LC Catalogers’ Desktop” 1 , provides guidelines for assigning 

subject headings to library materials. It emphasizes procedures in practical terms, so it is especially useful 

to libraries engaged in cooperative projects with the Library of Congress. 

<strong>NLM</strong> uses this manual primarily as a reference tool to compare subject cataloging practices. 

1 Available online via a subscription through the LC Cataloging Distribution Service (see 

http://www.loc.gov/cds/desktop/). 


II.B. General Policies 

1. When to assign subject headings 

Assign subject headings, as appropriate, to all materials being cataloged. 

2. Determination of primary/secondary subjects 

Identify the subject headings assigned to an item as either primary or secondary, according to these 

definitions. 

The primary heading or headings represent the main topic of the item being cataloged, and in 

combination with a publication type, if applicable, lead to the assignment of a particular classification 

number for the item. A direct link between the primary subject heading(s) and the classification number 

can be established in the majority of cases (excluding, for example, the primary subject of an individual 

analytic of an analyzed multipart set). 

Prefer one primary subject heading per item. In cases where the main topic of the work cannot 

adequately be covered by one primary heading (e.g., there is no single pre-coordinated subject heading, 

or main heading topical subheading combination available that links to an appropriate classification 

number), two or three primary subject headings may be assigned. 

For example, a work on fire prevention in hospitals requires the coordination of the MeSH term 

Fires qualified by prevention & control, and the MeSH term Hospitals, to link to the appropriate 

classification choice, “WX 185,” used for hospital safety, fire and disaster programs in the <strong>NLM</strong> 

classification scheme. 

All other subject headings, not directly linked to the classification number chosen, are identified as 

secondary subject headings. 

3. Order of subject headings 

List subject headings in order of their importance: primary subject heading(s) first, followed by any 

secondary subject headings. 

4. MARC coding 

Topical main headings are recorded in the MARC 650 $a, using the second indicator “2” to show that they 

come from the MeSH thesaurus. Primary subject headings are coded with a 650 first indicator of “1”, 

secondary subjects are assigned the first indicator of “2.” 


Geographic terms are recorded in MARC 651 $a. The first indicator is blank, and second indicator is 2. 

The only topical subheadings that may be appended to the 651 are $x ethnology and $x epidemiology. 

Geographic terms are found in the MeSH Z tree. 

Topical subheadings are recorded in subfield $x of the 650 or 651 fields. Subfield $x is not repeatable. No 

other subfields are used with 650 and 651 fields. 

Publication types (PTs) are recorded in the MARC 655 $a field with the first indicator blank, and second 

indicator of 2. No other subfields are used with the 655 field. Publication Type terms are found in the 

MeSH V tree. 

5. Transcription of MeSH headings 

MeSH headings and subheadings are input exactly as found in the MeSH Heading field of the MeSH 

Browser in regard to capitalization, punctuation, inversion, etc. 

II.C. Assigning MeSH Terms 

1. General 

a. Contents of the item 

Assign subject headings that accurately and completely describe the contents of the item. Cover all 

important aspects of the item, (i.e., that represent at least 20% of the content) without redundancy. To 

the extent possible, use the most specific subject headings that apply. Use judgment in determining 

whether subject access should be provided for preliminary or background information (e.g., chapter(s) on 

the anatomy or physiology of a system, in a work about diseases of that system). 

b. Serials and multipart items 

For serials and incomplete multipart items (i.e., in cases where <strong>NLM</strong> does not yet own all volumes), use 

judgment in determining how specific the subject analysis should be. Examine the volume(s) being 

cataloged to discover any available information about forthcoming volumes. If it appears that the volumes 

will cover a wide range of subjects, prefer one or two general subject headings to a great many specific 

headings. 

c. Broader or narrower relationships 

Use judgment in applying both broad and narrower terms from the same tree. Using both broad and 

narrower terms from the same tree may be appropriate in cases where half the content of the material is 

very general or applies to the tree as a whole, but special emphasis in the work is given to one or two 

narrower concepts. 


d. Assigning the same MeSH term 

It may sometimes be appropriate to assign the same MeSH term two or three times in a bibliographic 

record, qualified by different topical subheadings, to bring out specific aspects of the topic discussed. It 

may also be appropriate to assign the same MeSH term once without qualification and again with a 

topical subheading, when half the content is about the MeSH term in general and the remainder is about 

one or two specific aspects of the subject. 

e. Audience 

In general, do not assign a subject heading for the audience or purpose for which the work is intended 

unless the content includes material specific to the audience or purpose. 

For example, the MeSH term Dentistry should not be assigned to a general work entitled 

Physiology for Dentists unless it includes specific information related to dentistry. However, 

Dental Care or a similar term would be appropriate to another work with the same title that 

does include information on how physiology specifically relates to dental procedures. 

This same principle applies to material written for a particular purpose. 

For example, the MeSH term Education, Continuing should not be assigned to an item intended 

to be used in a continuing education course, unless it also discusses how to design a continuing 

education course or provides other information on the specific concept of continuing education. 

f. Patient care terms 

Use judgment in assigning patient care terms (e.g., Ambulatory Care, Aftercare, Palliative Care, etc.) as 

coordinates to specific disease, procedural, or therapy terms. Generally restrict the use of these terms to 

cases where (1) the care is unusual in the specific situation; or (2) the care is specifically discussed in 

detail. 

2. Main headings 

a. General 

Main headings, or descriptors, represent the subject content of items being cataloged. For very general 

works, one or two main headings may reflect the content completely. For more specialized works, 

subheadings may be added to pinpoint specific aspects of the concept represented by the main heading. 

Assign the most specific heading or headings available that describe the contents of the work. Applying 

the following guidelines, use as many specific main headings as needed to cover the major subject 

content of the work. That is, assign specific headings, as needed, to cover what is discussed in at least 20% 

of the work, not merely mentioned. 


. Rule of three 

Up to three individual specific MeSH terms, which are indented under the same broader heading, may be 

used. If more than three specific terms in the same tree are needed, assign the broader heading instead. 

This applies only to MeSH terms that are found in the same tree. In all other cases, assign specific MeSH 

headings as needed. 

c. Diseases vs. specialty 

Read MeSH annotations and scope notes and examine the tree structure carefully to determine whether 

a term is defined as a disease, specialty, procedure, or other concept, and for guidelines suggesting other 

appropriate terms. 

For example, the MeSH term Thoracic Surgery represents the surgical specialty. The MeSH 

annotation says “a surg specialty” and leads the user to the term Thoracic Surgical Procedures 

which should be used for the procedure. 

Carefully consider whether a work is about a disease or a specialty or both. 

For example, a work entitled Textbook on cardiology might be about: 

Heart diseases and related disorders; the appropriate MeSH term for that work is Heart 

Diseases OR 

Cardiology as a field or profession, covering such topics as trends, history, economics, 

and education; the appropriate MeSH term for that work is Cardiology. 

If the subject matter is about the disease or diseases, use the disease heading(s) along with any 

appropriate therapeutic or procedural terms. If the subject content is about the profession or field, use 

the specialty heading. If both disease and specialty concepts are discussed, use both terms. 

Note: in a very few cases, a specialty term may be used for diseases as well, when no specific disease term 

exists. Read MeSH annotations carefully to determine whether a specialty term may be used for a disease 

or other concept, or whether a related disease term is available. 

Examples: Pediatrics is annotated “SPEC; when permitted for ‘pediatric dis” with a link to the 

Indexing Manual for more specific instructions. It may be used for pediatric diseases for which no 

appropriate MeSH term is available. Cardiology is annotated “SPEC” and is used only for the 

specialty. See Related references are provided for specific diseases. Aerospace Medicine is 

annotated “specialty; med, physiol or psychol aspects of AVIATION go here but med, physiol or 

psychol aspects of space flight go under SPACE FLIGHT or other space related terms.” A link to 

the Indexing Manual is provided for a more detailed explanation. 

d. Pre-coordinated organ-disease terms 


When a pre-coordinated organ-disease concept does not exist in MeSH, coordinate the organ term and 

the most specific disease term available. 

For example, since no MeSH term exists for diseases of the Cystic Duct, and Cystic Duct trees 

under Bile Ducts, cystic duct diseases are represented by the coordination of Cystic Duct and Bile 

Duct Diseases. Cystic duct neoplasms are represented by the coordination of Cystic Duct and Bile 

Duct Neoplasms. 

In some cases, the MeSH annotation provides coordination instructions; however, the principles of 

coordination apply, even when there is no instructional annotation. 

e. Diseases vs. organisms 

Do not confuse organisms with the diseases they cause. For example, Salmonella is a type of bacteria and 

is treed in B3 (Bacteria). The MeSH annotation provides the information “infection = Salmonella 

Infections or its specifics.” For the disease concept, use Salmonella Infections” or a more specific term 

which trees under Salmonella Infections. 

f. Biographies 

For biographies, assign the MeSH term for the appropriate class of persons, e.g., Physicians or the 

relevant specialty. For example, use General Surgery for a biography about a surgeon. Add personal 

names as subjects for single or collective biographies covering up to three people. Use judgment about 

adding names as subjects for more than three people in unusual situations. Use also the publication type 

Biography or Personal Narratives as explained in the section "Special Instructions for the Use of Certain 

Publication Types.” 

g. History 

The terms History of Medicine, History of Dentistry, and History of Nursing are used for very general 

works on these topics. Works on the history of specific topics are represented by the most specific term 

available, qualified by the topical subheading history. For example, a work on the history of 

psychoanalysis is represented by the MeSH term Psychoanalysis qualified by history. (See also II.C.3 

Topical Qualifiers/Subheadings) 

For works about the History of Medicine or a more specific historical topic in a particular time period, 

coordinate the historical term with the appropriate time period (e.g., History, Medieval; History, 16 th 

Century). 


EXAMPLES: 

A general work on the history of medicine in ancient times is represented by coordination of the 

subjects: 

650 12 $a History of Medicine 

650 22 $a History, Ancient 

A work on the history of obstetrical practices in the 18 th century is represented by the 

coordination of the subjects: 

650 12 $a Obstetrics $x history 

650 22 $a History, 18 th Century 

h. MeSH annotations (General) 

Use caution in assigning MeSH terms that have the Indexing annotation " almost never IM." In cataloging, 

it may be appropriate to use these terms in some situations; consider carefully whether the concept is 

significant enough in the content to deserve subject access. It is the cataloger’s responsibility, not only to 

help the user find appropriate material on any given subject, but also to help the user eliminate material 

that merely mentions, but does not discuss the desired topic. 

Generally, headings annotated: “Not used for indexing” should not be used by catalogers, with the 

exception of specified manifestation headings, (e.g., Eye Manifestations, Neurologic Manifestations, etc.) 

that are used by catalogers. 

Headings annotated: “Check tag only” (e.g., Male, Female, Mice, etc.) are not used by catalogers. 

Headings that may be used either as a check tag or as a MeSH concept are annotated “NIM as check tag” 

along with specific instructions for use. These terms, which include age groups and Pregnancy, are used in 

cataloging. 

Headings annotated: “used for searching: indexers and catalogers apply specifics” (e.g., Amino Acids, 

Peptides, and Proteins) should not be used by catalogers. 

Headings annotated: “used for searching: indexers apply specifics; may be used by catalogers” (e.g., Body 

Regions) are permissible for use in cataloging. 

Headings annotated: “GEN: avoid: prefer specifics” OR “avoid: too general; prefer specifics” (e.g., 

Autonomic Agents, Animal Structures, etc.) may be used by catalogers if more specific term(s) are not 

available or appropriate. 

i. Pharmacologic actions 

Many substances are known to have multiple functional aspects or pharmacological actions (PA). For 

works about the action of a drug or chemical, use the respective drug/substance MeSH heading and the 

MeSH heading for the pharmacologic action(s) being studied. 


EXAMPLE: 

A work about the ability of aspirin to prevent platelets clumping together: 

650 12 $a Aspirin 

650 22 $a Platelet Aggregation Inhibitors 

j. Supplementary concept records (SCRs) 

The MeSH Browser also contains records for substances which are not included as descriptors in the 

MeSH vocabulary. These supplementary concept records are not considered main headings or used as 

subject headings. In assigning a main heading, use the MeSH term(s) that appears in the field labeled 

“Heading Mapped to.” Supplementary concept records are easily recognized because in the MeSH 

browser the label for the term is Name of substance, rather than MeSH Heading and the term itself is all 

in lower case letters. 

EXAMPLE: 

Name of substance: salicin 

Heading Mapped to: Benzyl Alcohols 

650 12 $a Benzyl Alcohols 

k. Age groups 

Age group MeSH terms and Pregnancy are entered on bibliographic records as main headings. They may 

function either as primary concepts or as secondary concepts, in coordination with other MeSH terms, to 

specify the age group or state of pregnancy in relation to the other term. 

When a term designating an age group or pregnancy is the primary focus of a work, it is coded as a 

primary heading. For example, for a work about a newborn infant as a physiological, psychological, or 

social entity, code the MeSH term Infant, Newborn as a primary heading. Also code these terms as 

primary when the classification choice is dependent on the coordination of the age group or pregnancy 

with another primary concept. (See III.C.1.d. Topics coordinated with Age Groups and Pregnancy) Use 

allowable qualifiers as appropriate with both primary and secondary age group and pregnancy concepts. 

EXAMPLES: 

060 10 $a WS 420 

650 12 $a Infant, Newborn $x psychology 

650 12 $a Infant, Newborn $x physiology 


060 10 $a WT 150 

650 12 $a Mental Disorders 

650 12 $a Aged 

060 10 $a WQ 240 

650 12 $a Mental Disorders 

650 12 $a Pregnancy 

3. Topical qualifiers/subheadings 

a. General 

Topical qualifiers or subheadings are used to narrow the focus of a main heading to a particular aspect of 

the subject, such as the diagnosis or therapy of a disease, the physiology or pathology of an organ, 

metabolism of a drug, or economics of providing a service. Assign the appropriate subheadings as required 

by the content of the work being cataloged, subject to the scope notes and annotations for the main term 

and subheadings, and according to the guidelines provided below. 

b. Allowable qualifiers (AQs) 

A complete alphabetical list of qualifiers is available at http://www.nlm.nih.gov/mesh/topsubscope.html. 

Qualifiers by allowable category are available at http://www.nlm.nih.gov/mesh/topcat.html. Note that 

the list of allowable qualifiers (AQ) in a MeSH Browser main heading record contains all the subheadings 

that are permitted with a given heading. Generally, no more than three topical subheadings are used with 

a single main heading. If more than three aspects of a main heading are discussed, choose broader 

subheadings from the Topical Subheading Hierarchies list 

(http://www.nlm.nih.gov/mesh/subhierarchy.html). 

For example, use the broader subheading physiology for a work that discusses the genetics, 

immunology, metabolism, and physiopathology of a topic; use therapy for a work that discusses 

diet therapy, drug therapy, nursing, and surgery for a given condition. When a work is so broad 

that more than three subheadings are appropriate, even when the subheading hierarchy is 

considered, use the main heading without subdivision. 


c. Entry combinations 

See references and annotations frequently link to related terms that are to be used in place of, or in 

addition to, a main heading or main heading subheading combination. Pre-coordinated terms to be used 

in place of a Main Heading/subheading combination are identified as “entry combinations” (EC) in the 

MeSH record. Annotations also lead to appropriate specialty terms. For example, Orthopedics has the 

Entry Combination “nursing:Orthopedic Nursing.” 

d. Annotations about qualifiers/subheadings 

Treat annotations such as "coord with organ /physiol" as guidelines on the correct subheading to use if 

pertinent, rather than as absolute instructions to be followed automatically. 

e. Common subheading coordinations 

Coordinate subheadings when appropriate. For instance, if a work discusses both the adverse effects of a 

substance and the diseases the substance causes, assign subject headings that bring out both these 

aspects, (e.g., Substance $x adverse effects and Disease $x etiology). Refer to the Indexing Manual, 

Chapter 19, for a listing of common coordinations of subheadings that can be useful in retrieval. 

f. Use of adverse effects, poisoning, and toxicity 

In distinguishing between the qualifiers adverse effects, poisoning, and toxicity: use the qualifier adverse 

effects for unintended harmful side effects of a substance or procedure in normal use; use the qualifier 

poisoning for severe or life threatening systemic effects of a substance, whether through environmental 

exposure, overdose, accident, or error; use the qualifier toxicity for experimental studies on the effects 

and margin of safety of drugs, chemicals, and environmental agents, and for non life threatening exposure 

to environmental agents. 

g. Use of epidemiology and ethnology 

Use the qualifier epidemiology for items that discuss distribution of disease and factors which cause 

disease, as well as for surveys and morbidity in certain geographic areas. The content may include 

discussion of incidence, frequency, prevalence, and/or endemic and epidemic outbreaks. Also use the 

qualifier epidemiology with the pertinent geographic heading, when epidemiology, ethnology, or mortality 

are used as topical subheadings with disease terms. 

Use the qualifier ethnology with diseases and selected terms for ethnic, cultural, and anthropological 

aspects and with geographic headings to indicate the place of origin of a group of people living outside 

their native land. Use the qualifier epidemiology with the pertinent geographic heading to indicate 

diseases in the place the ethnic group is currently living. 

EXAMPLES: 


For a work on alcoholism in Inuits living in Alaska: 

650 12 $a Alcoholism $x ethnology 

650 22 $a Inuits 

651 2 $a Alaska $x epidemiology 

For a work on diabetes in Mexicans living in England: 

650 12 $a Diabetes Mellitus $x ethnology 

651 2 $a Mexico $x ethnology 

651 2 $a England $x epidemiology 

Note that epidemiology and ethnology are the only two subheadings that can be used with geographic 

(651) subject terms . 

Do not use the general headings Ethnic Groups or Continental Populations Groups when the topical 

subheading ethnology is used; however, if a specific ethnic or population group is discussed, add the 

appropriate term. If the qualifier ethnology is not allowed with the pertinent main heading(s), coordinate 

with Ethnology as a main heading. 

h. Use of legislation & jurisprudence 

Use the qualifier legislation & jurisprudence for laws, statutes, ordinances, or government regulations, as 

well as for discussion of law, legal controversy, and court decisions. When legislation & jurisprudence is 

not allowed with a particular main heading, for text or discussion of law, coordinate with an appropriate 

legislation main heading, such as Legislation or Legislation, Drug or Legislation, Food. Coordinate with 

Jurisprudence as a main heading for works on the application of the principles of law or discussion of 

court cases. Additionally, use the publication type Legislation when 20% percent or more of the content 

consists of the text of law. Use the publication type Legal Cases for works consisting of reports of decided 

cases and documents related to those cases. 

i. Use of history 

The qualifier history is used for works discussing the historical aspects of a subject. It is not used for 

materials on a topic written as contemporaneous works or for reprints of such works, simply because they 

are old. 

EXAMPLES: 


For a work describing the history of military nursing during the American Civil War, 

written in 2003, use: 

650 12 $a Military Nursing $x history 

650 12 $a American Civil War 

For a work on nursing in the Confederate Army of Tennessee published in 1866 and 

reprinted in 1998, use: 

650 12 $a Military Nursing 

650 12 $a American Civil War 

651 2 $a Tennessee 

j. Use of metabolism, pharmacokinetics, and pharmacology 

In distinguishing between the qualifiers metabolism, pharmacokinetics, and pharmacology as subheadings 

under drug terms: use the qualifier metabolism for discussion of what the body does to a chemical; use 

the qualifier pharmacokinetics for a discussion of how an exogenous chemical travels through the body; 

use the qualifier pharmacology for the chemical's effect on the body. 

k. Use of statistics & numerical data 

Use the qualifier statistics & numerical data with non-disease terms for expressions of numerical values 

which may be provided in graphic, tabular, or narrative form. For works that cover statistical aspects of a 

disease, use topical subheadings epidemiology, ethnology, or mortality, as appropriate. Other topical 

subheadings are also used to cover statistical information on specific subjects. For example, for statistics 

on economic aspects of a particular subject, use the qualifier economics. Other topical subheadings used 

for statistical data include manpower, supply & distribution, and utilization. Consult the subheading scope 

notes in the MeSH Browser and Chapter 19 of the Indexing Manual for guidance on selecting the 

subheading appropriate to the particular aspects encompassed in the work being cataloged and verify 

that the selected term is an allowable qualifier with the pertinent main heading. When statistics & 

numerical data, or a more specific statistical subheading, is needed with a term for which it is not an 

allowable qualifier, coordinate with Statistics as a main heading. Additionally, use the publication type 

Statistics when 20% or more of the content consists of statistical data. Also use the publication type 

Tables when 50% or more of the material is presented in tabular form. 


l. Use of radiography, radionuclide imaging, surgery, and ultrasonography 

Use judgment in deciding whether to use the subheadings radiography, radionuclide imaging, surgery, 

and ultrasonography with an organ term or with the precoordinated organ disease or injury term. If the 

work being cataloged discusses investigation of complaints or symptoms that may be indicative of a 

disorder, generally use the organ term. If it is known that a disorder is present, use the pre-coordinated 

disease or injury term. In some cases, both terms may be appropriate. 

m. Coordinating a general subheading with a more specific main heading 

Consider coordinating a general subheading with a more specific main heading to bring out the specific 

aspect of the subheading discussed. For example, for a work discussing microsurgery of the lens, 

coordinate the subject heading Lens, Crystalline $x surgery with the main heading Microsurgery. 

However, do not coordinate a specific subheading with a more general main heading (e.g., do not use the 

general MeSH concept Diagnostic Imaging in coordination with a main heading qualified by the more 

specific subheading ultrasonography). 

4. Geographics 

When the scope of a work is limited to particular geographic areas, assign the appropriate MeSH 

geographic name headings. Geographic terms are recorded in MARC 651 $a. The first indicator is blank, 

and second indicator is 2. Only geographic terms found in the Z tree of MeSH are valid for use as 

geographic subjects. 

The only topical subheadings that may be appended to the 651 are $x ethnology and $x epidemiology. 

Do not use geographic headings unless the content is limited to a particular area or areas. For example, do 

not use Wisconsin or United States for a study performed in a Wisconsin hospital, unless the discussion is 

limited to what happens in Wisconsin, or with the broader heading, what happens in the United States. 

In general, use a maximum of three geographic headings on a bibliographic record. When more headings 

seem important for retrieval purposes, four may be used. Consider also using a broader heading if one is 

available. For example, use Europe when four or more European countries are discussed. Use Appalachian 

Region when four or more states treed under Appalachian Region are discussed. 

Use geographic headings, whenever applicable, for individual and collective biographies and 

autobiographies when the assigned subject headings include a specialty or named group. 

Geographic headings append to all assigned subjects in distribution. 

For instructions on using geographic names as corporate subjects, see II.D.6.Geographic names. 

5. Genre/publication type headings (PTs) 

a. General 


Genre/publication type headings (PTs) are used to indicate what an item is as opposed to what it is about. 

The complete list of publication types with scope notes is found in online at 

http://www.nlm.nih.gov/mesh/pubtypes.html. Publication types appear as the “V” tree of the MeSH 

vocabulary and may be searched using the MeSH Browser. 

Publication types (PTs) are recorded in the MARC 655 field with the first indicator blank, and second 

indicator of 2. <strong>NLM</strong> catalogers may occasionally use publication types from other sources such as Archival 

Moving Image Materials (AMIM) or a local list. These are coded 655 with a first indicator of blank, and 

second indicator of 7 and a $2 with the source of the term. 

There are many MeSH heading/publication type pairs. The topical main MeSH heading is used when the 

work is "about" certain topics/subjects. It has the phrase "as Topic" at the end of the heading. The 

parallel publication type identifies the form of the information presented. For example, Clinical Trials as 

Topic is used for works about design, methodology, economics, etc. of clinical trials, while the publication 

type Clinical Trial is used for original reports of the conduct or result of a specific clinical trial. 

b. Annotations and scope notes for publication types 

All PTs have the annotation “this heading is used as a Publication Type.” All publication types in the MeSH 

vocabulary may be used by catalogers unless they are annotated “CATALOG: do not use” or “Not used for 

indexing or cataloging” or there is an annotation restricting usage such as “CATALOG: do not use for 

current materials.” The lists of publication types used by Cataloging and the History of Medicine Division 

(HMD) are available at http://www.nlm.nih.gov/tsd/cataloging/catpubtypes.html. 

Assign appropriate genre/publication type headings according to the scope notes. 

c. Multiple publication types 

Multiple publication types may be assigned. If more than one publication type heading is applicable, 

assign them in order of importance, i.e., the one that corresponds to the classification form number 

should be listed first (see section III.E.2. General Guidelines for the Use of Form Numbers). 

d. Use of $9 n with publication types 

When <strong>NLM</strong> records are distributed to licensees, publication types append to the existing subject strings as 

650 $v. To prevent a publication type from appending to a particular subject heading, <strong>NLM</strong> uses the 

coding $9 n after the subject heading. 


It may be appropriate to repeat a MeSH term, used once with and once without a publication type 

appended for distribution. For example, for a work on Liver Diseases, where half of the text provides 

substantive information in addition to describing illustrations, and half consists of pictorial works, use the 

650 Liver Diseases twice and append a $9n to one of the headings. For a work that gives both biographical 

information and history of the person’s field, use the specialty heading once without any topical 

subheading. Allow the publication type Biography or Personal Narratives to append. Repeat the specialty 

heading with the qualifier history and do not append the publication type, by supplying a $9n. 

EXAMPLES: 

650 12 $a Liver Diseases 

650 22 $a Liver Diseases $9 n 

655 2 $a Atlases 

650 12 $a Physicians 

650 22 $a Epidemiology $x history $9 n 

655 2 $a Biography 

650 12 $a Surgery 

650 22 $a Surgery $x history $9 n 


e. Special instructions for use of selected publication types 

• Atlases: Use for collections of illustrative plates, charts, etc. and for items in which there are both 

illustrations and text, even when the text predominates, when the purpose of the text is to explain the 

illustrations. Do not use for geographic atlases or maps. For maps, use the publication type Maps. 

• Case Reports: Use for reports of clinical cases in connection with diseases or medical specialties, as well 

as for single case reports in clinical medicine. Do not use for institutional case reports. Use instead the 

MeSH topical heading Organizational Case Studies. 

• Catalogs: Use for works consisting of lists of items arranged in some definite order, which describe the 

resources of a collection, including the holdings of a library, items in a museum, etc. Catalogs also include 

lists of materials prepared for a particular purpose, such as exhibition catalogs, sales catalogs, medical 

supply catalogs, etc. 


• Collected Works: Use for collections of articles that are identified as having been previously published in 

one or more sources. 

• Congresses: Use for proceedings of a conference, works that are "based on a conference" or that consist 

of "expanded (updated) papers from a conference," or "abstracts of papers from a conference.” For works 

that are "based partly on a conference" or identified as an “outgrowth of a conference,” use judgment in 

determining whether the work contains substantial material from the conference and assign or omit the 

publication type Congresses accordingly. If the item contains only one or two papers originally presented 

at a conference or a personally authored summary of a congress, do not use the publication type 

Congresses. In case of doubt, do not assign the publication type Congresses. 

• Dictionary: Use for reference works containing lists of words, usually in alphabetical order, giving 

meaning, and frequently including information about form, pronunciation, etymology, and grammar. Use 

with relevant specialty main headings for comprehensive lists of terms important in special fields. See also 

Encyclopedias and Terminology. 

• Encyclopedias: Use with relevant specialty main headings for reference works containing informational 

articles, usually arranged in alphabetical order. 

• Essays: Use for collections of articles that have not been previously published, and that are identified by 

the author or editor as "essays.” Use Collected Works for collections of previously published articles. 

• Exhibitions: Use for works describing an exhibition. Use the MeSH term Exhibits with the publication 

type Catalogs for exhibition catalogs. 

• Legislation: Use for text of laws, statutes, ordinances, or government regulations. Do not use for works 

that are merely discussion of laws. 

• Nurses' Instruction: Use for background material on diseases and other topics written for a nursing 

audience, which do not include specific nursing procedures. Do not use as a substitute for the topical 

subheading nursing when that subheading is not an allowable qualifier for a given MeSH term. Instead, 

coordinate with the main heading Nursing Care or another appropriate nursing term. Do not coordinate 

Nurses' Instruction with other nursing concepts and do not append Nurses’ Instruction to any main 

heading or main heading subheading combination that already contains the terms "nurse" or "nursing." 

• Personal Narratives: Use for single as well collections of autobiographical accounts and personal 

reminiscences. 

• Phrases: Generally used for works for non-native speakers of a language, containing common terms, 

phrases, idioms, and typical conversations, e.g., between a health professional and patient. See also 

Terminology. 

• Statistics: Use when 20% or more of the content consists of statistical data. 

• Tables: Use for any kind of data that is presented in tabular form. For statistical data presented in 

tabular form, use both Statistics and Tables. 


• Terminology: Use for technical terms or expressions used in a specific field. These lists may or may not 

be formally adopted or sanctioned by usage. See also Dictionary and Phrases. 

For full list of Publication Types used by Cataloging and the History of Medicine Division, see 

http://www.nlm.nih.gov/tsd/cataloging/catpubtypes.html. 

6. Language subheadings 

Language information is recorded in MARC 21 field 041. In distribution, the language(s) encoded in MARC 

21 field 041 $a, append to the subject string (MARC 21 field 650) in subfield $x when any of the following 

publication types are used: Dictionary, Encyclopedias, Phrases, or Terminology. 

II.D. Assigning Other Subject Added Entries 

1. General 

a. Names/uniform titles from Name Authority File (NAF) 

Assign subject access, as appropriate, for any names or uniform titles discussed in the work being 

cataloged. The headings for these names must be created according to cataloging rules and practices, in 

conformance with the latest revision and updates of the Anglo-American Cataloguing Rules, 2nd ed., 

(AACR2) and established in the <strong>NLM</strong> authority file. 

Do not use corporate names or uniform titles from the MeSH vocabulary. In MeSH, these types of 

headings are generally annotated "CATALOG: use NAF entry". [If a name or uniform title is not so 

annotated, bring it to the attention of a Cataloging Section MeSH representative.] 

Headings annotated: “Coordinate with specific NAF entry if applicable” may be used by catalogers in 

addition to the specific NAF entry. 

Note also that the names of some specific laws are included in the MeSH vocabulary. These terms are not 

used by catalogers and are annotated "CATALOG: use NAF entry". Catalogers are to enter laws as subjects 

using the appropriate jurisdiction name as a corporate subject (MARC 21 field 610) with the authorized 

name of the law provided in $ t. 

b. Use of topical subheadings with names/uniform titles 

Do not use topical subheadings with corporate, personal name, or uniform title subject added entries. 

c. Coordination of names/uniform titles and MeSH 

Generally coordinate with the appropriate MeSH term for the type of corporate entity, named group, or 

specialty, with applicable subheadings. 


EXAMPLES: 

Assign subjects to a history of the American Academy of Nursing as follows: 

610 22 $a American Academy of Nursing 

650 12 $a Societies, Nursing $x history 

Assign subjects to a biography of Michael DeBakey as follows: 

600 12 $a DeBakey, Michael E. $q (Michael Ellis), $d 1908- 

650 12 $a Cardiology 


Assign subjects to a work about the National Institutes of Health as follows: 

610 22 $a National Institutes of Health (U.S.) 

650 12 $a United States Government Agencies 

2. Personal names 

For works that are about an individual and/or the individual's work, assign the appropriate heading for 

that person in correct AACR2 format in MARC 21 field 600. In cases where a MeSH term exists for the 

person's theories (e.g., Jungian Theory), use judgment in determining whether both the MeSH term and 

the heading for the person are appropriate. 

3. Corporate names 

For works that discuss a corporate entity, assign the appropriate heading for that corporate name in 

correct AACR2 format in MARC 21 field 610. 

When a work discusses a corporate body that has undergone name changes over time, generally assign 

only the heading used by the body during the latest period covered by the work being cataloged. If the 

body was well known by an earlier name and that name is featured prominently as a subject of the work, 

assign the heading for the earlier name as well. 

Generally do not assign corporate subject access to a work about the holdings of a corporate body. 

Rather, assign a main or added entry for the corporate name, since the body is the source (author) of the 

holdings. 


4. Conference names 

For personally authored or edited works about a conference, not authorized by the conference 

committee, assign the heading for the conference name, in MARC 21 field 610 or 611, as appropriate, in 

correct AACR2 format. Do not use the publication type Congresses. 

5. Uniform titles and name/title entries 

For works that discuss another bibliographic work (e.g., a criticism or explication, etc.), assign the 

appropriate heading for the uniform title in correct AACR2 format. Enter it as a uniform title subject (in 

MARC 21 field 630) if the work itself is entered under title according to AACR2 rules. If the work itself is 

entered under a personal, corporate or conference name, enter the uniform title in $t in the appropriate 

6XX field for the author as subject. 

6. Geographic names 

In the rare instance of a work that discusses only a geographic entity (e.g., an area handbook or statistical 

survey of one area, with a title such as Area Handbook for Zambia), assign the appropriate heading for the 

geographic name as a corporate subject in correct AACR2 format in MARC 21 field 610. However, 

distinguish between items that actually discuss the geographic entity and those that merely identify a 

geographic aspect of a MeSH concept, e.g., Malaria control in Botswana, where the geographic concept is 

recorded in a 651 field. 

II.E. Special Situations in Subject Cataloging 

1. Editions 

In general, revised editions of a work are assigned the same subjects as those used on the previous 

edition, unless one or more of the exceptions below apply. 

Exceptions: 

• When the scope and content of the material has changed, assign subjects appropriate to the 

current edition. 

• When more specific MeSH terms have been added to the MeSH vocabulary, assign the most 

specific terms available that are appropriate to the new edition. 

• If cataloging policies have changed, follow the policies in effect at the time of cataloging the 

current work. 

• If the previous edition was given limited cataloging and the current edition is being cataloged at 

the full or BSR/CSR level, assign all subjects appropriate for full or BSR/CSR level cataloging. 


Note: If no subject is coded primary on the bibliographic record for the previous edition, do not assume 

that the first listed subject was intended to be the primary subject. Determine the primary subject based 

on the current work. 

Do not change subjects used on an earlier edition to match those used on the new edition if the earlier 

edition was correctly cataloged according to policies and available MeSH vocabulary at the time of 

cataloging. Use judgment in determining whether cataloging should be revised if it was incorrectly done 

according to the rules and subjects available at the time of cataloging. Correct egregious errors. 

2. Translations 

In general, translations are assigned the same subjects as those used on the original work, unless one of 

more of the exceptions below apply. 


• When new more specific MeSH terms have been added to the MeSH vocabulary, assign the 

most specific terms available that are appropriate to the translation. 

• If cataloging policies have changed, follow the current policies in effect at the time of 

cataloging the translation. 

• If the original work was given limited cataloging and the translation is being cataloged at the 

full or BSR/CSR level, assign all subjects appropriate for full or BSR/CSR level cataloging. 

Note: If no subject is coded primary on the bibliographic record for the original work, do not assume that 

the first listed subject was intended to be the primary subject. Determine the primary subject based on 

the current work. 

Do not change subjects used for the original work to match those used on the translation if the original 

was correctly cataloged according to policies and available MeSH vocabulary at the time of cataloging. 

Use judgment in determining whether cataloging should be revised if it was incorrectly done according to 

the rules and subjects available at the time of cataloging. Correct egregious errors. 

II.F. <strong>NLM</strong> Subject Analysis -- Historical Practices and Changes 

1. Assignment of subject headings 

Until the mid-1980s, <strong>NLM</strong> generally assigned subject headings only to materials published within twentyfive 

years of the date of cataloging. From the mid-1980s until July 1996, <strong>NLM</strong> restricted subject heading 

assignment to materials with imprints of 1914 or later. Subject headings were first assigned to reprint 

editions of 19th century materials (original imprints of 1801-1913) beginning in March of 1989. Until July 

1996, subject headings were generally not provided for modern editions and criticisms of works originally 

published before 1801. 


Until 1996, subject headings were assigned to the following materials regardless of original imprint date: 

(a) reference materials, including individual or collective biographies, bibliographies, directories, etc.; (b) 

statistical documents; and (c) works about institutions, societies, etc. 

Subject headings are now assigned to all materials cataloged by <strong>NLM</strong>. 

2. Order and priority of subject headings 

Prior to the mid 1990s, subjects were listed alphabetically and the primary subject was not indicated. 

3. Change to internal structure of subject strings 

Beginning with the implementation of the 1999 MeSH and the Integrated Library System, the <strong>NLM</strong> 

Cataloging Section changed the internal structure of its subject strings to facilitate cross-file searching and 

provide consistent retrieval results in <strong>NLM</strong>'s various web based databases. In conformance with indexing 

practice, catalogers began limiting qualification of MeSH descriptors to topical subheadings. 

Through 1998, geographic, language, and form subheadings were included in <strong>NLM</strong>’s local subject string 

when applicable, and distributed to bibliographic utilities and other licensees in the same format as that 

used internally. Additionally, catalogers used topical subheadings to qualify relevant main headings with 

age groups or pregnancy, whereas indexers used check tags to convey these concepts. 

Catalogers began to provide age group and pregnancy terms as main MeSH headings in 1998, using the 

same terms as those used by indexers. At the same time, catalogers began to store geographic headings 

separately in the Geographic Name Field, MARC 21 field 651, and not as part of the subject string. 

Additionally catalogers discontinued providing a language subfield for dictionaries, encyclopedias, phrase 

books, and terminologies. A language code is provided separately in MARC 21 field 041, as well as in the 

fixed fields. 

Through 1998, form subdivisions were included as part of the subject string in 650 $v by <strong>NLM</strong> catalogers 

to indicate the physical or intellectual characteristics of a work, representing what the item is as opposed 

to what it is about. Additionally, form subheadings were used to indicate the physical carrier of an item, 

such as videocassette or audiotape. Form subheadings representing the genre of a work were replaced in 

1999 by Genre/Publication type headings, provided in <strong>NLM</strong> bibliographic records internally in MARC 21 

field 655 and local field 659. Physical carriers were not converted to publication types, but instead began 

to be represented in the coding and physical description of an item, no longer supplied in the subject 

heading string. 

Although the internal subject structure for cataloging at <strong>NLM</strong> was retrospectively changed for all titles in 

the <strong>NLM</strong> catalog, <strong>NLM</strong> continued to provide its subject string in a more traditional form (i.e., 650 $a $x $z 

$v $l) in records distributed to bibliographic utilities and most licensees. In <strong>NLM</strong> distributed records, age 

headings and publication types were combined with MeSH headings to produce a traditional subject 

string from 1999 through 2005. 


4. Notable changes in subject analysis practice since 2006 

a. Age Groups and Pregnancy 

Beginning with the implementation of MeSH for 2006, age groups and pregnancy headings are provided in 

the same format on distributed records as in <strong>NLM</strong>’s local files. Age groups and pregnancy are not 

appended to the subject string on distributed records. 

Prior to 2006, when age groups or pregnancy were coded as secondary subjects (MARC 21 field 650 22) 

they were attached to other specially coded main headings or main heading and topical subheading 

combinations on records distributed to the bibliographic utilities, such as OCLC, and other <strong>NLM</strong> licensees. 

b. Publication Types 

Beginning in 2006, all MeSH Publication Types (PTs) used in cataloging are entered in MARC 21 field 655 

and may be appended to the subject string on distributed records. 

Prior to 2006 a distinction was made between PTs which had previously functioned as form subheadings 

and those which had never been used as form subheadings. PTs which had never functioned as form 

subheadings were entered in <strong>NLM</strong>’s local field 659 and not attached to the subject string on distributed 

records. 

<strong>NLM</strong>’s local field 659 is no longer used. All MeSH PTs used by cataloging may be appended to the subject 

string as form subheadings (650 $v) on distributed records. A local subfield (650 $9 n) is appended to the 

subject string as an instruction to the computer to prevent PTs from attaching inappropriately on 

distributed records. For a fuller explanation and examples see section II.C.5 Genre/Publication Type 

Headings (PTs). 

For information on creating traditional subject strings in a local catalog see 

http://www.nlm.nih.gov/mesh/catpractices.html#CreatingTraditional. Also, instructions for 

reconstructing MeSH subjects on <strong>NLM</strong> MARC 21 distributed records are available at 

http://www.nlm.nih.gov/tsd/cataloging/unstringmesh.html. 

III. Assigning Classification 

III.A. Basic Tools 

1. National Library of Medicine Classification 

The <strong>NLM</strong> Classification (http://www.nlm.nih.gov/class/ ) is an alphanumeric scheme for the arrangement 

of library materials by broad subject categories, similar to that used by the Library of Congress (LC). The 

scheme is a system of mixed notation, where alphabetical letters denoting subjects are further subdivided 

by numbers. It covers medicine and related sciences, utilizing schedules QS-QZ, and W-WZ, ranges not 

used by LC. 


The latest version of the National Library of Medicine Classification can be found at 

http://www.nlm.nih.gov/class/. It is updated annually. 

See also the introductory material to the classification, which provides an explanation of classification 

practices, at http://www.nlm.nih.gov/class/nlmclassprac.html. 

2. Library of Congress Classification Schedule 

The various schedules of the Library of Congress Classification (http://www.loc.gov/catdir/cpso/lcco/ ) are 

used to classify subjects peripheral to medicine and for general reference works. 

Specifically, <strong>NLM</strong> uses LC classification for psychology, science, sociology, veterinary medicine, and other 

subjects bordering on medicine. LC’s QM (Human Anatomy), QR (Microbiology), and R (Medicine) 

schedules are not used since they duplicate coverage of the <strong>NLM</strong> classification. QL (Zoology) and QP 

(Physiology) numbers are used only for works on wild animals. Works on human anatomy, physiology, 

etc., and on laboratory and research animals are classed in the appropriate <strong>NLM</strong> schedule. Works on 

domestic animals and veterinary medicine are classed in the appropriate LC schedules. 

The LC classification schedules, LC Classweb, are available online by subscription at 

http://classweb.loc.gov/. 

3. Classification Course: Cataloging: Fundamentals of the <strong>NLM</strong>® Classification 

The course (http://www.nlm.nih.gov/tsd/cataloging/trainingcourses/classification/index.html ) is a free 

set of modules and interactive exercises that students may take at their own pace without an instructor. 

The course is divided into nine modules: Overview of the <strong>NLM</strong> Classification, Using the Online <strong>NLM</strong> 

Classification, Components of <strong>NLM</strong> Call Numbers, General Principles, Table G, Form Numbers, 

Bibliographies and Related Materials, Classification of 19th Century Works and Early Printed Books, 

Continuing Resources. 

III.B. Basic Rules 

1. When to assign classification numbers 

Assign a classification number to all print and non-print materials cataloged. 

Beginning in January 1994, the majority of newly cataloged print monographs, exclusive of reference titles 

and materials destined for the History of Medicine Division (http://www.nlm.nih.gov/hmd/index.html), 

are assigned accession numbers for shelving in the <strong>NLM</strong> collection. As of 2004, audiovisuals are shelved by 

accession number in the general collection. All audiovisuals shelved in Reference or in the History of 

Medicine Division are assigned <strong>NLM</strong> classification numbers. The audiovisuals are then shelved together by 

class number and media code. 


In addition to the accession numbers, <strong>NLM</strong> also assigns an alternate classification number for 

monographs, as well as for serial analytics classed with the serial in the form numbers, W1 and W3 (see 

III.E.4. Serial Publications). Fully shelflisted call numbers, with cutters and dates, are only supplied for 

material in the Reference or History of Medicine collections. 

Microfiche issued by the Superintendent of Documents are assigned the SUDOC number for classification. 

An alternate call number is not provided. 

2. Principles of classification 

a. General 

For print and non-print monographs, classed serials, electronic and integrating resources, the 

classification number assigned to a work is determined by the primary subject content or focus of the 

work and represents as closely as possible the primary MeSH heading or headings selected. Other 

materials and serials, in particular, are classified by form (see III.E. Special Rules and III.E.4.Serial 

Publications). 

A work dealing with several subjects that fall within different areas of the classification is classed by 

emphasis, or if emphasis is lacking, by the first subject treated in the work. 

b. Classification by disease, region, organ 

A work on a particular disease is classified with the disease that, in turn, is classified with the organ or 

region chiefly affected, regardless of special emphasis on diet, drug, or other specific form of therapy or 

diagnostic procedure. However, if the work is about a drug, special form of therapy, diagnostic procedure, 

or environmental condition as a cause of disease, etc., and the disease is only mentioned in the context of 

the primary subject (the therapy, etc.), classify as always for the primary subject. 

A work dealing with a particular region of the body or organ system is classified with the region or organ 

system, depending on the emphasis of the work. For example, a general work on the region of the Head 

and Neck is classified with the Musculoskeletal System in the WE schedule. However, when the emphasis 

concerns dental problems and procedures related to the mouth, teeth, and jaws, the work is classed in 

WU with Dentistry. If the emphasis is concerns the otolaryngological problems and procedures, related 

to the ear, nose, and throat, the work is classified in the WV schedule with Otolaryngology. If the 

emphasis is on the Brain and associated organs, the work is classified in WL with the Nervous System. 

c. Choosing between the <strong>NLM</strong> and LC Classification schedules 

In some cases, a term is indexed to numbers in both the <strong>NLM</strong> and the LC classification schedules, 

depending on emphasis. If medical aspects predominate, classify the work in the <strong>NLM</strong> schedule. If social, 

religious, or other aspects predominate, classify in the LC schedule. In case of doubt, prefer the <strong>NLM</strong> 

schedule. 


EXAMPLE: 

A general work on social problems related to abortion is classified in the LC schedule 

general works number for induced abortion, HQ 767-767.52. 

A work on medical issues and procedures related to abortion is classified in the <strong>NLM</strong> 

schedule number for induced abortion, WQ 440. 

In some cases, even if the medical aspect does not predominate in the content of the work, the work is 

classified for the medical portion of its content because that is the content relevant to the <strong>NLM</strong> collection. 

EXAMPLE: 

A general botany text that includes information on medicinal plants or medicinal uses of 

plants is classified for the medical portion of the content. 

For more guidance on deciding between the <strong>NLM</strong> and LC classification numbers, see the section on the 

Library of Congress schedules in <strong>NLM</strong> Classification Practices at 

http://www.nlm.nih.gov/class/nlmclassprac.html#Library. 

d. Pediatrics 

Classify in the WS schedule works on diseases of specific body systems in children, as well as works on 

diseases limited to the newborn or premature infant. Classify works on anatomy or physiology of the child 

in QS or QT, works on topics other than body systems per se, with the topic (e.g., surgery of the child in 

WO 925), and works on specific diseases in children with the disease (e.g., pneumonia in infants in WC 

202). 

e. Humans vs. animals 

If the emphasis is human medicine, classify with the medical aspect in the <strong>NLM</strong> schedule. For example, a 

work discussing cancer research using laboratory animals in order to learn what causes cancer in humans 

is classified in QZ with works on the etiology of cancer in humans. In general, prefer classification with 

human medicine. For materials that discuss both humans and animals, prefer classification with the 

human. 

When an animal is discussed in connection with research, classify in QY under the specific number for the 

animal, if available, or the general number for Animals, Laboratory, if no specific number is available. 

For materials that discuss both humans and animals, prefer classification with the human. 

f. Reversal of a medical procedure 

Generally class the reversal of a medical procedure in the same number as the procedure itself, if no 

separate number exists. 


g. Biography vs. autobiography 

For works that are biographical or autobiographical in nature, consider the emphasis of the work. If it is 

primarily an account of a professional person in a given medical or other related field, generally classify in 

WZ 100. If it is a personal narrative relating to an individual's experiences with a disease, specialty, etc., 

or, if there is generally a heavier emphasis on the subject than on the person, classify with the subject. 

h. Verification of class numbers in the index 

Always verify classification numbers that are found in the index with the actual listing in the schedules, 

since there may be annotations, expansions or other important information that can influence the choice 

of classification. It is important to read annotations, provided at the beginning of the range of numbers 

being considered, for instructions that apply to the schedule as a whole. 

i. Geographic subdivision 

Geographic subdivision is provided for certain subjects and publication types in the <strong>NLM</strong> classification 

schedules by the application of Table G (see Table G instructions in section III.C.1.e.). The use of 

geographic breakdown is restricted to those classes which are annotated “Table G” and is appropriate for 

both monographs and serials. Table G information is recorded as part of the class portion of the call 

number. See further instructions in section III.C.1.e. 

3. Structure of the classification number and MARC coding 

When the classification portion of the call number consists of a single letter and a single digit, it is entered 

without any space (e.g., W1, W2, W3, etc.). All other classification numbers are entered with a space 

between the letters and the numbers (e.g., W 4A, W 15, WB 1, WB 5). See also “Shelflisting Procedures 

for Monographs and Classed Serials” at http://www.nlm.nih.gov/tsd/cataloging/shelf.html. 

Note: This spacing convention also applies when <strong>NLM</strong> assigns a classification number from the LC 

classification schedule (see also III.D.2. Using the LC Classification Schedule). 

All class numbers used by <strong>NLM</strong> are recorded in the 060 field with a second indicator of 0 (zero) including 

LC class numbers used by <strong>NLM</strong>. The first indicator of 0 (zero) means that the item is shelved at <strong>NLM</strong> at 

that number. First indicator of 1 means that the item is not shelved at <strong>NLM</strong> at that number. 

EXAMPLE: 

060 10 $a HV 11 

650 22 $a Social Work $x education 


III.C. General Procedures for Assigning the Classification Number 

The class number chosen should represent, as nearly as possible, the primary subject or subjects of the 

material being cataloged, as modified by a topical subheading when appropriate, or, in some cases, by the 

form or type of material being cataloged. 

Selecting Classification Number for Primary Subject 

1. Using the class schedule index 

After assigning MeSH, look up the primary subject in the index of the <strong>NLM</strong> Classification. 

a. Specific concepts 

Some subjects may be indexed to a specific number (e.g.: Reticulocytes to WH 150). 

Always refer to the main schedule to verify the number to be certain there are no annotations directing 

the cataloger, in specific circumstances, to use another number. 

For example, Dental Materials is indexed to WU 190. The main schedule, at WU 190, contains the 

annotation, “General or not elsewhere classified.” Above this number in the schedule, WU 180 contains 

the annotation “Dental alloys and metals.” If the work is on dental metals, for which there is no MeSH 

term, it should be classed at WU 180. 

b. General concepts 

Subjects of a general nature are usually indexed to a section of the class schedule (e.g., Mental Disorders 

to WM) or a range of numbers (e.g., Kidney Diseases to WJ 300-378). Refer to the section of the class 

schedule to which the primary subject is indexed and select the most appropriate number. If the subject is 

not listed, or the primary focus of the work includes several subjects within the schedule, or is very 

general, select the class number annotated “General Works” (e.g., a general work on dentistry is classified 

in WU 100). 

c. Classification modified by topical subheading 

When a topical subheading is used with the primary subject, check both the class schedule index and the 

main schedule to determine whether a specific number has been assigned to cover that aspect of the 

topic. 


Whenever a main heading/topical subheading concept is indexed to a specific number in the class 

schedule that matches the primary main heading/subheading chosen, use that class number, unless a 

form number is required (see III.E.2.General Guidelines for the Use of Form Numbers). For example, a 

general work on Kidney Diseases is classed in WJ 300, but a work on Kidney Diseases qualified by 

diagnosis is classed in WJ 302. A general work on Acquired Immunodeficiency Syndrome is classified in 

WC 503. Acquired Immunodeficiency Syndrome qualified by therapy is classed in WC 503.2. 

Always verify numbers selected from the index in the main schedules because there may be an 

appropriate specific class number that is not listed in the index to the classification. Read all annotations 

and examine the schedule for expansions. 

EXAMPLE: 

In the index under Kidney the cataloger is led to WJ 300-378. Specific numbers for $x anatomy 

and $x physiology are not provided, but an examination of the schedule leads the cataloger to 

WJ 301 for Kidney $x anatomy or Kidney $x physiology. The cataloger is led to the same range of 

numbers for Kidney Diseases as for Kidney, but must read the schedule to determine that Kidney 

Diseases $x radiography is classified in WJ 302. 

d. Topics coordinated with age groups and pregnancy 

Some subjects have specific classification numbers for particular age groups and the state of 

pregnancy. For example, general works on Mental Disorders are classified in WM 140, but general works 

on Mental Disorders in adolescents are classed in WS 463, in infants and children in WS 350, in the aged 

in WT 150, in pregnancy in WQ 240. 

e. Applying geographic subdivision 

Supply a “Table G” geographic Cutter for all classification numbers that are annotated “Table G” in the 

<strong>NLM</strong> Classification. Instructions for applying “Table G” geographic Cutter numbers are provided in the 

introductory material to the <strong>NLM</strong> Classification at 

http://www.nlm.nih.gov/class/TableGPractices.html. The “Table G” geographic Cutter tables are 

provided at http://www.nlm.nih.gov/class/TableGOutline.html. 

Note that most geographic Cutter numbers consist of two letters and one or more numbers; take care not 

to confuse a letter “I” with a number “1”, or a letter “O” with a number “0”. 

Table G geographic Cutters represent the latest name of the geographic entity, when names have 

changed over time. 

If there is no Table G geographic Cutter for a particular country, consult the Class Team Chair or 

designated Unit Head. 


If the classification number selected to represent the primary subject is annotated “Table G”, the 

cataloger must also provide one or more geographic headings in the MARC 21 field 651 representing the 

dominant area or areas discussed. If more than one geographic area is discussed, list first the geographic 

heading for the entity that is emphasized, and, in the absence of emphasis, to the one treated first in the 

work. (See also II.C.4. Geographics.) 

The Table G geographic Cutter number selected must correspond to the geographic heading provided in 

the first MARC 21 field 651 on the bibliographic record. 

For every number in the schedule annotated “Table G”, there is a corresponding number annotated “Not 

Table G” used for works on the same topic that have no geographic emphasis. 

EXAMPLE: 

EXAMPLE: 

A work on the Quality of Health Care in Maryland is classified in W 84.4 AM3, whereas a work 

on the Quality of Health Care with no geographic emphasis is classified in W 84.41. 

A medical directory that includes listings primarily from one country and one or two other 

countries is classified in W 22 with the appropriate Table G geographic Cutter for the 

predominant country. A medical directory that includes more than three countries is classified in 

W 22.1, if no one country predominates. 

A directory listing physicians primarily in the United States, with a few listings for Canada is 

assigned the Table G geographic Cutter for the United States 

Do not use a Table G geographic Cutter with any classification number that is not annotated 

“Table G”, even though the primary subject of the work to be classified may have a geographic 

emphasis for which a 651 geographic heading is assigned. 

For numbers that provide both Table G/Not Table G options, if a MARC 21 field 651 Geographic 

Heading is not used, select the classification number annotated “Not Table G”. 

f. Using LC classification numbers referenced in the <strong>NLM</strong> Classification index 

If the primary subject chosen falls outside the field of medicine, the <strong>NLM</strong> class schedule index may refer 

the cataloger to a number or range of numbers in the LC classification schedule. When the primary 

subject is indexed to a range of numbers, check the range and select the most appropriate number within 

it. If the subject is indexed to a single specific number, verify the LC schedule to be sure the number is still 

appropriate. Portions of the LC schedule have been updated since the publication of the latest <strong>NLM</strong> 

schedule. 


III.D. Selecting a Class Number When the MeSH term is Not Listed in the <strong>NLM</strong> Class Index 

1. Using the MeSH tree structures 

a. General 

Check medical terms, names of drugs, etc., in the MeSH Tree Structures of the MeSH Browser to locate 

the broader term under which the primary MeSH term is treed, and generally assign the classification for 

the broader term. 

EXAMPLE: 

The MeSH term Parasomnias is not in the <strong>NLM</strong> class index. The term is found in the Tree 

Structures under the broader term Sleep Disorders. Sleep Disorders is indexed to WM 188. 

Classify Parasomnias in WM 188. 

To be certain that the classification for the broader term is appropriate, read the scope note for the 

chosen term and for that of the next higher term in the tree. Compare the context in which the term is 

used in the item being cataloged with the MeSH scope note and tree category. Use judgment in 

determining whether the classification for the next higher term is appropriate. 

When a term is in multiple trees, consider the context in which it being discussed and the most important 

characteristic of the subject. For example, Cockayne Syndrome trees under both Dwarfism and 

Neurodegenerative Diseases. In determining the appropriate classification, consider the most important 

aspect of the topic discussed and classify for that aspect. 

For class numbers where there is a detailed A-Z breakdown (e.g., Collective biography by specialty, WZ 

112.5; specific DNA viruses, QW 165.5, etc.), when a specific number does not exist which represents the 

subject of the work being cataloged, classify the work by looking in the index to the classification for the 

MeSH term that is the next higher term in the MeSH tree. 

EXAMPLES: 

The term Mastadenovirus is not provided in the classification index 

Mastadenovirus trees under Adenoviridae 

Adenoviridae is classified in QW 165.5.A3 

Classify works on Mastadenovirus in QW 165.5.A3 

The term Circoviridae is not provided in the classification index. 

Circoviridae trees directly under DNA Viruses 

Since no A-Z number is provided for Circoviridae, works on Circoviridae are classified with the 

broader term DNA Viruses QW 165. 


. Drugs and chemicals 

Special care must be used in classifying drugs and chemicals. Often the term or the next higher term in 

the tree leads to a number in LC’s chemistry schedule (QD) or <strong>NLM</strong>’s biochemistry schedule (QU). If the 

context of the work is about the action of the substance and not its chemical makeup, coordinate with the 

appropriate Pharmacologic Action term (e.g., Anti-Bacterial Agents, Anti-Allergic Agents, etc.), code both 

subjects primary and classify for the type of agent. 

EXAMPLE: 

Natamycin trees under Macroslides (neither term appears in the index), which in turn trees 

under Lactones. Lactones is indexed to a number in QD in LC’s chemistry schedule. However, if 

the item being cataloged is about Natamycin as an antifungal antibiotic and not about its 

chemical makeup, it should be classed with Antibiotics, Antifungal in QV 252. 

When a chemical is discussed as treatment for a specific disease, class with the disease. 

When a chemical is discussed as a multipurpose drug, beneficial in the treatment of many diseases, 

coordinate with Pharmaceutical Preparations and class at QV 55. 

When the chemical discussed is from a plant coordinate with the appropriate plant term, e.g., Plant 

Preparations, Plant Extracts, or Phytotherapy, and class for the plant term. 

EXAMPLE: 

For a work on multiple therapeutic uses of a preparation made from Salix, a substance which comes from 

willow bark. 

060 10 $a QV 766 

650 12 $a Salix 

650 12 $a Plant Preparations $x therapeutic use 

2. Using the LC Classification schedule 

For terms outside the fields of medicine, not listed in the <strong>NLM</strong> class schedule index, search for an 

appropriate class by checking the primary subject or a similar term from LC Subject Headings in LC’s class 

schedule and indexes. 


III.E. Special Rules 

1. Bibliographies, abstracts, and indexes 

For bibliographies, abstracts (the publication type used for annotated bibliographies), and indexes falling 

within the scope of the <strong>NLM</strong> class schedule, use the appropriate subject oriented <strong>NLM</strong> class number 

prefaced by the letter “Z”. 

For example, works on Chronic Disease are classified in WT 500. A bibliography of works on Chronic 

Disease is classified in ZWT 500. 

Works falling outside the scope of <strong>NLM</strong>’s class schedule are classed in LC’s Z Schedule. 

For conference publications containing abstracts, give the publication type Congresses (not also 

Abstracts) and do not prefix the call number with Z. 

2. General guidelines for the use of form numbers 

Some materials are classed for form or publication type (e.g., Atlases, Dictionaries, Outlines) or for the 

specific aspect of the subject discussed (e.g., education, history, legislation), rather than for the particular 

subject used. In these instructions, the term “form” is used to mean both publication type and specific 

aspect of material. 

Within each main schedule the numbers 1-39 are used for form. Some main schedules are divided into 

sections with form numbers in each section. Within the QV schedule for Pharmacy, for instance, form 

numbers QV 701-735 are used instead of the numbers QV 1-39 that are used for the rest of the 

Pharmacology schedule; form numbers WO 1-39 are used for Surgery, WO 200-233 for Anesthesia. Form 

numbers are the same in most, but not all schedules. 

Always consult the appropriate section of the main schedule and read the annotations before assigning a 

form number. 

When a form number is appropriate, use the form number from the main schedule that covers the 

primary subject. For example, a work on Liver Neoplasms is classed in WI 735. An atlas of Liver 

Neoplasms is classed in WI 17, along with all other atlases falling within the Gastrointestinal System 

schedule. A work on Psychoanalysis is classed in WM 460. Psychoanalysis $x history is classed in WM 11, 

along with all the other histories falling within the psychiatry schedule. 

In general, a form number applies to any subject that falls within a particular classification 

schedule. Assign the appropriate form number unless the work is on a specific topic, and the form 

number is annotated “General” or has an instruction such as “Classify works for special subjects with the 

subject.” 


Form numbers annotated “General” are used only for general works. An item on a specific topic within 

the schedule is assigned a topical class number. Form numbers 5, 7, and 9 in the various schedules are 

annotated “General” and are used only for collected works covering the whole schedule. A collected work 

on a specific topic is classed with the topic. 

EXAMPLE: 

A collected work by several authors, covering many aspects of obstetrics is classed in WQ 5 for 

collected works, but a collected work on Fetal Diseases is properly classed in WQ 211. 

The following is a representative, not exhaustive, list of form numbers from the <strong>NLM</strong> Classification and 

the corresponding publication type: 

Classification Numbers Publication Type or specific aspects 

11 History 

13 Abbreviations 

Dictionary 

Encyclopedias 

15 Classification 

Phrases 

Terminology 

16 Statistics 

Tables 

17 Atlases 

Pictorial Works 

18 Education 

18.2 Examination Questions 

Problems and Exercises 

Outlines 

Programmed Instruction 


22-22.1 Directory 

25 Laboratory Manuals 

32-33.1 Legislation 

39/49 Handbooks 

In addition to the form numbers used throughout the classification schedule, there are several separate 

form numbers for Popular Works in specific sections of the schedule (e.g., WG 113 for Heart Diseases, 

WQ 150 for Pregnancy, and QZ 201 for Neoplasms). 

When both a main heading and subheading have their own form numbers, generally classify for the 

subheading. 

EXAMPLE: 

060 10 $a WY 11 

650 12 $a Education, Nursing $x history 

For special exceptions on classification of historical works see III.E.6. Works on historical aspects of 

subjects. 

When both a topical subheading and a publication type are classed by form, classify for the publication 

type. 

EXAMPLE: 

060 10 $a WO 18.2 

650 12 $a Surgery $x history 

655 2 $a Outlines 

When more than one publication type is used, list first and classify for the one that is most important. 

3. Special Instructions for classification of Legislation and Statistics 

a. Legislation 

Classify in the form number for laws (generally 32) in the appropriate schedule for the primary subject 

when 50% or more of the content consists of the text of laws, statutes, etc. 


When the content of an item consists of discussion of law, etc., classify in the form number for discussion 

of law (generally 33) in the appropriate schedule for the primary subject. 

See also the section II.C.5.e “Special instructions for use of Certain Publication Types”, specifically use of 

the publication type Legislation. 

b. Statistics 

Classify in the form number for Statistics and Tables (generally 16 in whichever <strong>NLM</strong> schedule is 

applicable to the primary subject) when 50% or more of the content of the item consists of statistical data 

or is presented in tabular form (see section II.C.5.e Special instructions for use of Certain Publication 

Types, specifically use of the publication type “Statistics” and the use of the publication type “Tables”). 

4. Serial publications 

Serials are classified in the form number W1. 


� Government administrative and statistical reports are classed in W2. Integrated administrative 

or statistical reports on several hospitals under government administration are also classed in 

W2. 

� Hospital administrative and statistical reports, including reports of a single government hospital, 

are classified in WX 2. 

� Certain publication types, such as directories, handbooks, etc., issued serially, are classed in 

those form numbers used also for monographs. Numbers which may be used both for serials 

and monographs are identified in the classification schedules with the annotation “Used for both 

monographs and serials”. See section III.E.2. General Guidelines on the Use of Form Numbers. 

� Serial publications consisting of bibliographies, indexes, or abstracts are classed for subject, as 

are monographs, according to instructions given for monographs. See III.E.1. Bibliographies, 

Abstracts, and Indexes. 

� The W3 call number is no longer assigned to new publications. It was used in the past for 

numbered congresses. It only is used now on analytic records for issues of serially issued 

congress proceedings when the serial was originally assigned a W3 call number. If the serial title 

changes, the new serial title and its analytics are classified according to current policy. For more 

information on historical practices, see III.F. <strong>NLM</strong> Classification Assignment – Historical Practices 

and Changes. 


Table G is applied to serials classified in numbers annotated “Table G” in the same manner as 

monographs, according to the principles given in section III.C.1.e. Applying Geographic Subdivision. 

5. Serial analytics 

Serial analytics are classified and shelved with the serial publication. 

An alternate subject classification is provided for serial analytics classified in W1 and W3. 

Alternate call numbers are not provided for serials classified in W2 or for those classified in a form, 

bibliography, or topical number that is also used for monographs. 

6. Works on historical aspects of subjects 

In general, the form number 11 is used for works dealing with the historical aspects of all subjects falling 

within a section of the class schedule (e.g., WM 11 is used for Psychiatry $x history; Mental Health 

Services $x history; Psychotherapy $x history, etc.). 


� The history of a drug is classified with the drug. (See annotation under QV 11 of the <strong>NLM</strong> class 

schedule.) 

� W 11 and WB 11 are not used. Use instead the appropriate number in the WZ schedule. In rare 

exceptions, when there is no appropriate WZ number, the history of a topic is classed in the 

same number as that used for works on current practice in the W and WB schedules. 

� WB 900 is used for the history of special systems or Complementary Therapies; WB 905.6 

specifically for the history of Chiropractic. In the WB schedule, see the annotation at WB 11. 

� History of a single infectious disease is classed with the infectious disease and not in WC 11. In 

the WC schedule, see annotation at WC 11. 

� The history of a society is classified in form number 1 in any <strong>NLM</strong> schedule where applicable. See 

annotation in the class schedule index under Societies. 

� For history of schools, laboratories, hospitals, institutes, organizations, etc., class in the 

appropriate form number for the type of entity. For example, W 19 is used for the history of a 

medical school, QY 24 for the history of a laboratory, and WM 28 for the history of a psychiatric 

hospital. 

� Other exceptions occur in <strong>NLM</strong> schedules that are subdivided into sections. For example, within 

the QS schedule there are several numbers for history: QS 11 for Anatomy $x history; QS 511 for 

Histology $x history; QS 611 for Embryology $x history. 


� Other special exceptions are noted in the annotations for specific form numbers. For example, 

under WX 11, an annotation is provided to use WX 215 for the history of emergency or 

ambulance service. 

7. WZ Schedule 

The WZ schedule is used for works on the History of Medicine, for early printed works, and for several 

special types of publications. It is also used for translations and reprints of early works. Works are classed 

by period of coverage, locality, original publication date, etc., according to the annotations in the class 

schedule. 

Works on the history of a particular subject are classified with the subject, as discussed in the section on 

historical works. For example, history of surgery is classed in WO 11 (see section III.E.6.). 

Biographies are classed WZ 100-150 for persons in the medical field, preclinical sciences, and related 

fields. Biographies of persons in fields unrelated to medicine are classified in the appropriate LC schedule. 

Early printed books (pre-1801) are classed WZ 220-260. WZ 270 is used for Americana. See the class 

schedule for dates of coverage. At <strong>NLM</strong>, only catalogers in the History of Medicine Division use the 

numbers for early printed books, in the range WZ 220-270. 

Modern editions, criticisms, and translations of early (pre-1801) works are classified in WZ 290-294. 

The WZ schedule is also used for other special types of materials: WZ 30 for chronologies; WZ 305-350 for 

anecdotes, folklore, cartoons, medical writing, biographical clinics on famous persons, etc. Examine the 

schedule to become familiar with its scope. 

8. 19th Century Schedule 

There is a special schedule for 19th century publications, used for materials and reprints of materials 

originally published 1801-1914. The schedule is a simplified subject classification consisting of letters and 

the classification notations W1-6, W 600, WX 2, and the form numbers that appear throughout the 

schedule. 

When it is necessary to use an LC class number for work published in the 19th century, follow a pattern 

similar to that used in the <strong>NLM</strong> 19th Century Schedule. That is, assign or use only the letters of the LC 

schedule that represent the subject of the schedule, e.g., BF for Psychology, SF for Veterinary Medicine, 

etc. 

For instructions on the classification of reprints of early works, see section III.E.14. 

For instructions on the classification of translations of early works, see section III.E.13. 


9. Nursing materials 

Classify materials on clinical medicine, written as background material for nurses, with the primary 

subject. Use the publication type Nurses' Instruction. Use the WY schedule for works that include nursing 

procedures, the nurses’ role, and the nursing profession. For historical practice in classifying nursing 

materials, see III.F. <strong>NLM</strong> Classification Assignment – Historical Practices and Changes. 

EXAMPLES: 

Catalog a work on hypertension written as background material for a nursing audience, that does 

not include information on the nurses’ role as follows: 

060 10 $a WG 340 

650 12 $a Hypertension 

655 2 $a Nurses’ Instruction 

Catalog a work defining the nurses’ role in diagnosis and treatment of hypertension as follows: 

060 10 $a WY 152.5 

650 12 $a Hypertension $x nursing 

10. Documents on microform 

Assign subject classification for titles on microform which do not have a Superintendent of Documents 

(SUDOC) call number. Include a Table G geographic Cutter if appropriate (see section III.C.1.e.). For 

items containing a SUDOC number, use that number also as the <strong>NLM</strong> call number. 

For serial analytics on microform, provide a complete W1 call number as for print serial analytics. 

11. Electronic resources 

Assign a subject classification for electronic resources as for print documents. Include a Table G 

geographic Cutter if appropriate (see section III.C.1.e.). 

12. Editions 

In general, assign the same classification to new editions of a work as that on the immediately preceding 

edition. The same Cutter number is assigned if the title and the main entry have not changed (see 

shelflisting instructions for editions). 


If the original title was incorrectly cataloged, or if the contents have been revised to the extent that the 

original class number is no longer correct, or if a new more precise class number has become available, 

assign the class number that represents the contents more accurately. 

Do not revise the classification of earlier editions to match that of a later edition if the item was classified 

correctly at the time of cataloging, using available classification numbers and rules in effect at that time. 

Use judgment in determining whether an item was incorrectly classified according to the rules and 

classification available at the time of cataloging. Correct egregious errors. 

13. Translations 

In general, classify a translation with the original, unless a more appropriate number has been added to 

the classification schedule. Do not reclassify the original publication if it was correctly classified according 

to the schedule in use at the time. See also shelflisting instructions for translations in the "Shelflisting 

Procedures for Monographs and Classed Serials", (see 

http://www.nlm.nih.gov/tsd/cataloging/shelf.html). 

Classify translations of pre-19th century (pre 1801) works in WZ 290. 

Classify translations of 19th century (1801-1913) works, as well as translations of works published after 

1914, in the main schedule. 

14. Reprints 

In general, use the complete call number from the original. 

Classify reprints of pre-1801 works in WZ 290. 

Classify reprints of 19th century (1801-1913) works in the 19th Century Schedule. 

Classify reprints of 20th- 21st century (1914- present) works with the original, unless a more appropriate 

number has since been added to the classification schedule. Do not reclassify the original publication if it 

was correctly classified according to the schedule used at the time. 

Consider a modern compilation of reprints of pre-20th century articles or works to be a modern 

work. Classify collections of reprinted papers in the appropriate number for the subject. 

Reprints of several works that include publications from the 20th century or later are classed with current 

works. 

15. Supplements 

For works that are supplements to other titles (e.g., review manuals, study guides, updates, etc.) and for 

accompanying books that are dependent on another book to be of any value, assign the same 

classification and Cutter number as for the main work. (See also shelflisting instructions for 

supplements.) 


These instructions apply even if a publication type that might otherwise determine the classification is 

assigned to the supplement. In such cases, do not classify in a form number; use the classification 

number of the main work. 

EXAMPLES: 

Parent vol., published in l998 

060 00 $a 1998 F-521 

060 10 $a WB 105 $b E537 1998 

Supplement published in 1999 

060 00 $a 1999 J-524 

060 10 $a WB 105 $b E537 1998 Suppl. 1999 

These instructions do not apply to companion volumes. Classify works that are identified as "companion 

volumes" or "sequels" to another work appropriately for actual content, not necessarily paralleling the 

classification of the original work. 

III.F. <strong>NLM</strong> Classification Assignment – Historical Practices and Changes 

1. W3 

Prior to 1988, all numbered congresses and serially issued congress proceedings were classified in the 

form number W3. New serially issued congress proceedings are classified, as are other serials, in form 

number W1. The proceedings of numbered congresses, not cataloged as serials, are classified separately 

by subject. See: III.E.4 Serial Publications for more information on current practice. 

2. WY 

Prior to 1984, <strong>NLM</strong> classified background materials on clinical medicine written for nurses in the WY 

schedule, together with materials dealing with nursing procedures in special fields of Medicine. For 

current practice on classifying material written for nurses see: III.E.9. Nursing Materials. 

3. Shelflisting 

Prior to 2010, <strong>NLM</strong> provided a fully shelflisted call number for all print monographs receiving full, 

core or BIBCO Standard Record (BSR) level cataloging. Cutter numbers and dates are currently 

supplied only for material in the Reference or HMD collections.

NLM Policy on Subject Analysis and Classification - National Library ...

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